The results of Earth-bound lab experiments appear to back up the theory that dark lines on Martian slopes are created by water - though in an otherworldly manner, scientists said Monday.

A team from France, Britain and the United States constructed models and simulated Mars conditions to follow up on a 2015 study which proffered "the strongest evidence yet" for liquid water - a prerequisite for life - on the Red Planet.

That finding had left many scientists scratching their heads as the low pressure of Mars' atmosphere means that water does not survive long in liquid form. It either boils or freezes.

Under Martian pressure, they found, melting ice produced a liquid which boiled vigorously as it flowed downslope and filtered into the sand.

The evaporating water vapor blasted grains upward, creating ridges which collapse onto themselves when they become too steep, forming channels.

"The morphologies produced on the sandy slopes in these experiments are remarkably similar to the streaks observed on Mars," Wouter Marra of the geosciences faculty of the University of Utrecht in the Netherlands commented on the study.

"This process in which unstable boiling water causes grains to hop and trigger slope failures may underlie some of the active landforms observed on the Martian surface."

for an unprecedented close-up look at these dunes to see, in great detail, how the grains of sand shift. Scientists are trying to figure out mysteries such as why ripples appear larger on some Martian dunes than Earth ones, and why they're of a different texture. Read on to explore some of the most recent findings and past observations of Mars' mysterious dunes.

This is one of the first images ever of a rover next to a large dune on Mars. Previously, NASA Mars Exploration Rovers Spirit and Opportunity were by much smaller ripples. NASA is trying to learn more about how dunes, which are distinguished by steep flanks like the one pictured here, move about on Mars. The challenge is modelling Martian winds and sands, which are obviously not as well-known as what is found on Earth. Curiosity is on the lookout for evidence of sand slides,

In 2009, the Spirit rover was exploring Gusev Crater -- filled with fluffy regolith -- when it became mired in a sand trap nicknamed "Troy." While not technically a dune, scientific investigations of the region before Spirit got stuck and eventually died showed what sand can hide underneath. In this case, the rover was sitting atop a sulfate deposit, associated with a hydrothermal (steam) vent. The rover's demise showed how difficult it is to predict the composition of sand in even flat regions on Mars.

, in April 2010. The dunes pictured here are relatively modest -- just 20 centimeters (8 inches) tall. The brighter spot in the foreground is a rock outcrop. Opportunity's controllers changed its route to Endeavour after discovering sand ripples (larger than the ones pictured here) that could have posed a threat to the rover.

In 2014, the Mars Reconnaissance Orbiter's powerful camera, HiRISE, captured dunes in the extremely active area of Nili Patera. The dunes have been tracked moving an average of 1.7 meters (5.5 feet) in less than four Earth months, according to

Once again, this image shows the amazing extent of dunes on Mars. This image is of the formations in Bunge Crater, taken by NASA Mars Odyssey's thermal emission imaging system in 2006, covering a region about 14 kilometers (9 miles) wide. The dunes are moving towards the left of the picture in this perspective. Scientists are doing their best to understand these processes by using computer models and comparing these dunes with ones on Earth.

This ESA Mars Express picture shows dunes towering in Rabe Crater as high as 200 meters (656 feet) high, nearly twice the height of the Empire State Building. They're mostly made up of basalt (volcanic rock) and have complex geology, according to the European Space Agency: "Its flat floor has a number of smaller craters and large sunken pits within it. The bulk of the dune material sits atop the flat remnant of the original crater floor, but then some of it spills dramatically down into the pits below."